This invention relates to an electro-static tobacco separator, wherein fine tobacco particles can be separated from a mixture with equal size sand particles.
In the processing of tobacco, there is a byproduct which is termed offal. This offal consists of sand and tobacco particles sieved from the product during the various stages of processing and manufacture. It is desirable to recapture the tobacco fines for reuse as in reconstituted tobacco. However, difficulty has been encountered in separating the tobacco particles from sand, as it is only the tobacco fraction which is of value, and any sand present is destructive to reconstituting equipment.
Heretofore, one type of separator utilizes a fluidized bed, such as shown in U.S. Pat. No. 3,402,814. In this type of separator, a mixture of grains are given the same polarity with a collector disposed above the fluidized bed and an electro-static field extending between the fluidized bed and the collector. The grains are distinguished by their conductivity as they may be conductive or insulating, of different weight or differentially chargeable. The difficulty with this system is that the charge holding capacity of tobacco is extremely shortlived and furthermore, in the arrangement shown in the above mentioned patent, there is no provision for continuous operation with the continual removal of the light fraction from the heavy fraction.
Another type of separator involves using an induced air flow above a fluidized bed to sweep away the lighter fraction of particles which is airborne. However, the equipment and energy requirements for this type of equipment adds considerably to both the initial cost and the operating cost of the system. Thus, such an induced air flow arrangement has not proven ideal for the separation of fine tobacco particles from sand.
According to the present invention, there is provided a conventional vibrating conveyor, wherein a portion of the conveyor is enclosed and provided with a grid spaced a predetermined distance above the feeder pan. A separate conveyor or trough is disposed immediately adjacent the grid and extends beyond the discharge end of the feeder pan. The feeder pan and grid are oppositely charged and a mixture of sand and tobacco particles is fed onto the feeder pan. As the lighter tobacco particles become charged, they pass upwardly to the oppositely charged grid and drop into the trough disposed adjacent the grid. This trough is also vibrated so as to move the tobacco particles towards the discharge end of the trough. Tobacco particles which do not fall into the trough are recycled and a substantially complete separation of the tobacco particles from the sand is effected by the time the mixture reaches the discharge end of the feeder pan. The system is inexpensive, provides different discharge points for the sand and the tobacco particles and may be operated on a continual basis.
An object of the present invention is to provide an electro-static tobacco separator in which fine tobacco particles can be separated from sand particles while the mixture is passing along a conventional vibrating conveyor.
Another object of the present invention is to provide an electro-static tobacco separator in which a grid is placed above and parallel to a conventional vibrating conveyor and the conveyor and grid are oppositely charged so that the lighter tobacco particles of a mixture of tobacco and sand particles will pass from the conveyor upwardly to the grid and will be trapped in a trough provided adjacent the grid.
Other objects and many of the attendant advantages of the present invention will become more readily apparent upon consideration of the following detailed specification, when considered in connection with the accompanying drawing, wherein;